I would add von Cramm, Drobny, Trabert, Pietrangeli and Santana and Gimeno to the group. I personally rate, as quite all Germans do, von Cramm over Nuesslein. In the few matches between the two, von Cramm came mostly on top. The Santana-Pietrangeli matches are described by Rex Bellamy as concerts between two pianists of the highest class, say Horowitz and Rubinstein. I have seen very few clay results of Segura, his game must be suited to clay. Hoad and Laver did very well on clay, they were the only two players in history, who won the French, Italian and German triple in the same year. Laver may have been not so consistent as Rosewall on clay, but it could very well be, that he had the upper hand in their actual clay head to head, due to some European results in 1963/64. In the open era, they were 4-4 (Bournemouth, RG 1968 (both Rosewall), Amsterdam, RG 1969, Louisville 1970 (all Laver), Washington 1971 (Ro), Houston 1972 (La), Houston 1976, Ro) with the last match played at Houston (and won by Rosewall) in 1976.